Is the effect of the NAO on North‐east Arctic cod,Gadus morhua,recruitment stock‐dependent?

There is considerable interest in understanding the effect of the North Atlantic Oscillation (NAO) on recruitment to North Atlantic cod stocks. An earlier analysis of data for the North‐east Arctic cod stock showed that, while there is an empirical relationship between recruitment and the NAO over the period 1973–96, this relationship was absent over the period 1946–72. It has recently been suggested that the effect of the NAO on recruitment depends on the size of the spawning stock. Here, the possibility that this explains the earlier result for North‐east Arctic cod is tested and rejected.     

DNA‐analysis to monitor fisheries and aquaculture: Too costly?

Evidence from DNA‐analysis is commonplace in human criminal investigations, and while it is increasingly being used in wildlife crime, to date, its application to control and enforcement activities in fisheries and aquaculture has only been sporadic. Contemporary DNA‐analysis tools are capable of addressing a broad range of compliance issues, species identification, mislabelling of fish products, determining the origin of catches and the farm of origin of aquaculture escapees. Such applications have the potential to ensure traceability along the fish product supply chain and to combat consumer fraud and Illegal, Unreported and Unregulated fishing. Nevertheless, DNA‐analysis is not yet used routinely in investigations into compliance with fisheries and aquaculture legislation. One potential reason for this is that DNA‐analysis techniques may have been regarded as too expensive. However, costs have plummeted over the past decade prompting us to objectively assess whether the costs associated with routine use of DNA‐analysis techniques for fisheries and aquaculture control and enforcement activities do constitute an impediment. Based on a number of recent fisheries and aquaculture compliance investigations that incorporated DNA‐analysis, our results indicate that the use of genetic analysis was justified and worthwhile in all cases examined. We therefore conclude that the costs associated with DNA‐analysis do not represent a barrier to the routine adoption of DNA‐analysis techniques in fisheries and aquaculture compliance investigations. Thus, control and enforcement agencies should be encouraged to use such techniques routinely.     

Major long‐term changes in the ecology of the Ythan estuary,Aberdeenshire, Scotland; how important are physical factors?

1. Long‐term data sets on macro‐algae, sediment invertebrates, shorebirds and physical parameters are explored for the Ythan estuary, Scotland. 2. Coverage by macro‐algal mats has increased over the last 40 years with significant impacts on the distribution and abundance of benthic invertebrates and their shorebird consumers. Areas of the estuary worst affected by the mats now support fewer Corophium volutator, whilst the abundance of this and other species has increased in areas less affected by mats, possibly through enrichment by non‐local macro‐algal detritus. 3. Shorebird abundance increased between the early 1960s and the 1980s, possibly in response to enhanced invertebrate abundance in unaffected areas, but has declined since, as algal mats continue to spread. 4. The cause of the increased biomass of macro‐algae is contentious, but the present analysis shows that the increase is unlikely to be related to changes in the physical characteristics of the estuary, which appear to have remained fairly constant over at least the last 30 years. Copyright © 1999 John Wiley & Sons, Ltd.     

Is Pseudanodonta complanata the most vulnerable of widespread European species of unionids? An intense stress test leading to a massive die‐off

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Country‐wide analysis of large wood as a driver of fish abundance in Swedish streams: Which species benefit and where?

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How many fish use mangroves? The 75% rule an ill‐defined and poorly validated concept

Although mangroves are known to play a critical part in the lives and life histories of many fish species, these values have rarely been definitively quantified. Despite this, claims such as “an estimated 75% of commercially caught fish depend directly on mangroves” are common across a range of government and non‐government documents from around the world, to the extent that the idea that 75% or more of fish depend on mangroves has become a truism widely used to support the value of mangroves. I investigated the basis for these claims that I summarize as the “75% rule.” The “75% rule” is imprecisely defined, and invariably cannot be traced back to definitive scientific data. Moreover, the claim is illogical because we simply do not have adequate knowledge of how many fish occupy different habitats or even how many species of fish there actually are. Moreover, even when the simplest proposition, of how many species use mangroves, is tested using global data bases, the best estimates fall far short of 75%. Clearly, the “75% rule” is wildly inaccurate, unsubstantiated and, at least give our current knowledge and methods, impossible to substantiate. Mangroves are critical to many species but using an indefensible pseudoscientific paradigm such as this to support conservation efforts, management actions and legal decisions, greatly weakens any arguments that build upon it, putting at risk outcomes that rely on the integrity of the claim.     

Is fertility of hybrids enough to conclude that the two oysters Crassostrea gigas and Crassostrea angulata are the same species?

The distinction of the two cupped oysters Crassostrea gigas (Thunberg, 1793) and Crassostrea angulata (Lamark, 1819) into two species was chiefly due to their differing geographical distributions, C. gigas being present in Asia and C. angulata in Europe. Today it is commonly accepted that C. angulata and C. gigas are a single species according to morphological, genetic and F1 hybridization data. However, the demonstration of the fertility of their hybrids and the absence of any reproductive isolation remained to be investigated. Consequently, we studied the fertility of hybrids and sperm competition by performing three different experiments and producing G1 and G2 hybrid progenies between wild populations of C. angulata and C. gigas. Progenies showed very close developmental yields, at 24 hours after fertilization, according to dam taxa suggesting a strong maternal transmission of oocyte quality, but no reproductive isolation was observed between the two taxa. Significant decreases of developmental yields were noticed in C. angulata females with sperm competition, most probably due to early larval mortality. The fertility of hybrids C. angulata × C. gigas was demonstrated, which is further evidence that they are the same species. To definitively state the precise taxonomic classification of C. angulata and C. gigas, further studies are needed to (i) identify geographical zones where these taxa are in contact and (ii) assess their level of hybridization in these zones.     

Aphanomyces astaci presence in Japan: a threat to the endemic and endangered crayfish species Cambaroides japonicus?

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Can the presence of a large conspecific improve the production and welfare of groups of smaller self‐feeder competent rainbow trout?

This study examined the production and welfare effects of including a large self‐feeder competent rainbow trout, Oncorhynchus mykiss (Walbaum) (~665 g) in groups of smaller self‐feeder competent conspecifics (~234 g). Costs and benefits were examined for both welfare (aggression, fin damage, condition and mortality) and production (self‐feeder utilization and growth). The 8‐week experiment used six groups of small trout; three treatment groups containing a large trout and three control groups. After 4 weeks the large fish were removed from treatment groups and added to control groups, thus reversing the treatments. Whilst it was thought that the presence of a larger fish would suppress aggression in smaller conspecifics this did not occur. In fact aggression was significantly (P = 0.036) higher when large trout were present during the first 4 weeks. No significant differences were found between other welfare indicators, self‐feeder utilization or production parameters. From a production and welfare perspective these results suggest that with the exception of initially increasing aggression larger fish do not represent a significant benefit or risk to smaller conspecifics being cultured in self‐feeder equipped tanks, when all fish are self‐feeder competent.     

Responses of scallop biodeposits to bioturbation by a deposit‐feeder Apostichopus japonicus (Echinodermata: Holothuroidea): does the holothurian density matter?

The deposit‐feeding holothurians can reduce the negative impact of bivalve farming by feeding and reworking bivalve wastes (biodeposits) in the context of co‐culture. To test effects of the bioturbation by holothurians of different densities on bivalve wastes, a stocking density regime of the sea cucumber Apostichopus japonicus (35.4 ± 1.2 g, mean ± SE) was set at 0.0, 6.6, 13.2 ind m^?2, and responses of the biotic parameters including chlorophyll a concentration (Chl. a), bacterial biomass and the abiotic ones as oxidation‐reduction potential (ORP), organic matter (OM), organic carbon (OC), total nitrogen (TN) and organic phosphorus (OP) in biodeposits discharged by Japanese scallop Patinopecten yessoensis were investigated. Results showed that A. japonicus grew in a density‐dependent manner, and the density‐dependent effect on both biotic and abiotic parameters in biodeposits were also observed. Apostichopus japonicus stimulated a transfer process from reduction to weak reduction state of the biodeposits with a trend of higher density holothurians stimulating the process more. Furthermore, A. japonicus significantly controlled the bacterial abundance and Chl. a, as well as reducing the contents of OM, OC, TN and OP in the biodeposits. Yet, the response of abiotic parameters delayed rather than that of biotic parameters, underling the biotic parameters could be more sensitive to bioturbation than the abiotic ones. Our study suggests that the bioturbation of A. japonicus plays an important role in retarding organic waste accumulation and cleansing nutrients in bivalve farming wastes under co‐culture condition and the bioremediation capacity may be closely dependent on its stocking density in practice.     

Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845)

Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted.     

Can patch size and patch distance improve the recolonization of mussel‐seed beds exploited for aquaculture?

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The contribution of cephalopods to global marine fisheries: can we have our squid and eat them too?

Cephalopods are a key component of marine food webs, providing sustenance for myriad marine species. Cephalopods are also of increasing economic importance as evidenced by the rapid rise in their global landings over recent decades. If fisheries continue on this trajectory, conflicts may transpire among cephalopod and finfish fisheries, particularly in ecosystems where cephalopods are highly valuable both directly as a landed commodity and indirectly as prey for other harvested species. We provide the first measure of the ecosystem services that cephalopods contribute to fisheries in 28 marine ecosystems, both as a commodity and an ecological support service. We also evaluate how current demands on cephalopods compare to mid‐20th century conditions. We find that cephalopod contributions to fisheries vary widely, but are substantial in many ecosystems. Commodity and supportive services provided by cephalopods contributed as much as 55% of fishery landings (tonnes) and 70% of landed values ($USD). The contribution of cephalopods as a commodity was generally greatest in the coastal ecosystems, whereas their contribution as a supportive service was highest in open ocean systems. Further, the commodity and supportive services provided by cephalopods to fisheries landings increased in most of the coastal ecosystems between the mid‐20th century (years 1960–70) and contemporary periods (years 1990–2004), indicating the rising demand for cephalopods. Current demands have no historical precedent and ecosystems in which cephalopods are highly exploited as a targeted resource and as an ecological support service should be further evaluated to prevent the unsustainable development of marine fisheries within them.     

Concurrent rice‐shrimp‐crab farming systems in the Mekong Delta: Are conditions (sub) optimal for crop production and survival?

The Mekong Delta is the most important rice‐ and shrimp‐producing region for food and economic security in Vietnam. Rice‐shrimp farming is practised where salinity fluctuates substantially between wet and dry seasons. Research points to several potential risk factors for rotational systems, but how these link directly to both rice and shrimp production remains poorly quantified for systems that stock and harvest animals year‐round. We examined water and soil quality of 18 rice‐shrimp‐crab ponds, in which shrimp and crab are grown in both wet and dry seasons, in the Cà Mau Province of Vietnam. Multiple lines of evidence indicated that environmental conditions experienced by both rice and shrimp were suboptimal and contributed to low yields and survival. Year‐round cropping of shrimp and crab was associated with sustained suboptimal salinity, intensified by drought, for the wet‐season cultivation of rice. Although rice seedlings were sown in all 18 ponds, only three had a harvestable crop. Low shrimp production and survival was associated with sustained suboptimal water temperatures (too high), salinity (too high in the dry season and too low in the wet season) and dissolved oxygen concentrations (too low). Food availability and quality may also have affected shrimp production. Improving productivity of rice‐shrimp‐crab ponds in the study region may require (1) separation of rice and shrimp crops and improving efficiency of soil washing practices such that salinity conditions are more suitable for each when grown, and (2) management intervention to increase oxygenation of water, and the availability and quality of food for shrimp.     

Is the establishment of MPAs enough to preserve endangered intertidal species? The case of Patella ferruginea in Mal di Ventre Island (W Sardinia,Italy)

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When aquaculture restores and replaces an overfished stock:Is the conservation of the Species assured? The case of the scallop Argopecten purpuratus in Northern Chile

The fishery for Argopecten purpuratus in northern Chile, whichcollapsed because of overfishing, has been replaced by aquaculture of thespecies. In 1998, cultures produced 16,474 t, while the highest landings recorded inthe entire history of the fishery was in 1984 (one year after the 1983 ElNiño) with 5275 t. The figures for stock size of the species in the pastand at present, show that the wild stock of scallops today represents notmore than 10–15% of the total stock of the species within Chile, with mostof the individuals being kept in sea farms. Thus it is concluded that thescallop already represents a domestic species and, considering theoccurrence and development of selection practices in sea farms,biodiversity within the species appears to be at risk. With the developmentof culture practices over its entire range, there is little use in trying torecover a wild fishery for this scallop. It is urgent, however, that selectednatural beds be protected in order to preserve genetic diversity.     

The “tsunami break:” impact of the Great East Japan Earthquake and the accompanying tsunamis on the shell growth of the invasive clam-eating snail <Emphasis Type="Italic">Laguncula pulchella</Emphasis>

The Great East Japan Earthquake and accompanying tsunamis occurred on 11 March 2011, causing huge damage to marine organisms. The invasive naticid gastropod Laguncula pulchella (Euspira fortunei), which was introduced with the imported clam Ruditapes philippinarum from China and Korea, survived the earthquake. The “growth break line” observed on the shell surface in over 90% of the individuals collected in Matsushima Bay and Matsukawa-ura Lagoon after the tsunamis was examined by scanning electron microscopy. Each shell presented three layers before and three after the growth break. However, the fracture surface consisted of five layers—two prismatic and three crossed lamellar—around the growth break line. This suggests that shell formation temporarily ceased following the tsunamis and that the five-layered shell may have developed in response to the stress caused by the tsunamis. The newly formed middle layer became thinner after the “tsunami break,” which may be the result of a rapid change in the mineralization process, including rapid shell growth and/or repair. These results suggest that the damage to and forcible removal of habitats by the tsunamis was stressful for L. pulchella. A decrease in or the cessation of shell formation after a tsunami may be a common phenomenon in mollusks that inhabit tidal flats.     

A selective and low impacting traditional fishery,sustaining the economy of small coastal villages in central Mediterranean: Keep or replace the small‐scale driftnets?

Small‐scale driftnets (SSDs) have been historically used in the Mediterranean without major environmental concern. The introduction of large‐scale driftnets caused unwanted catches of protected species. Specific regulations were therefore issued in European waters, culminating in a proposed moratorium on SSDs. This study aimed to characterise the SSD fishery targeting anchovy (menaide), evaluating its environmental sustainability, economic performance and social relevance. In 2013, a survey by interviews, logbooks and observers on board assessed the order of magnitude of this fishery in terms of fishing capacity and activity, volume of landings and revenues. The menaide fleet consisted in 60 vessels <12 m overall length, moored in little harbours in southern Italy. These nets are highly selective: the target species, European anchovy, Engraulis encrasicholus (L.) and sardine, Sardina pilchardus (Walbaum), dominates the catches, while discards are negligible. The anchovies caught are of high quality and large size; the high prices support fish processing by local factories. Moreover, the results of a SWOT analysis demonstrated that replacing SSDs with a semi‐industrial fishery, like purse seining, would increase impacts on the ecosystem, and a loss of socio‐economic opportunities for several coastal villages. These findings support the option of keeping SSDs operating, in the framework of specifically oriented management measures.